It was a mystery in 2011 when a MRT train was found vandalised at the Bishan depot.
On Aug 17 that year, the words "JET SETTER'S" - measuring between 8m and 9m in length and 1m in height - were found spray-painted in blue on one side of the train carriage.
A hole was also found in the wire fence, but for years, the culprits remained unknown.
This was until a video surfaced online in April this year. It clearly shows two masked people breaking into the depot and vandalising the train.
The 4min 32sec clip was uploaded to a website which belongs to American couple Jim Clay Harper, 31, and Danielle Bremner, 34.
The grafitti artists had fled the US in 2011 while on probation for graffiti-related offences and went on a "spraycation" that took them to at least 10 countries, including Singapore.
In the write-up to the video on their exploits here, the duo make it clear that they were responsible for the Bishan depot vandalism and bragged about being the first ones to film an act of vandalism on a Singapore MRT train. The video was uploaded on April 28.
It starts off with a montage of news clips on the 2011 vandalism that show the seriousness with which Singapore treats such cases, followed by various shots of the Singapore cityscape and MRT trains in operation.
At the 1min 20sec mark, two people - presumably Harper and Bremner, each of their faces covered with a piece of gray cloth - appear with a plastic bag containing a wire cutter.
A third person films them moving about.
They cross a canal to a fenced area. Before using the wire cutter to cut a hole in the fence, they also show a "Protected Place" sign, which shows a figure with a rifle pointing at another figure with its hands up.
After they get inside, they use spray cans to vandalise an MRT train with the graffiti words: "JET SETTER'S" while referring to a sketch on a folded piece of paper.
Once done, they get a shot of the graffiti before leaving via the hole in the fence.
The Singapore video is one of at least 10 episodes that showcase the law-breaking artists.
But the law caught up with them recently.
Harper, 31, was jailed by a court in Melbourne, Australia, on May 31 for eight damage charges, attempted robbery and a recklessly causing injury charge.
He was nabbed earlier that month after a fight with a passer-by who tried to stop him putting stickers on shops in Fitzroy, a suburb in Melbourne, reported News.com.au.
Bremner, 34, is on the run and fled to Hong Kong, which is the location of the website's latest video.
A police spokesman told TNP yesterday that the Singapore Police Force is aware of Harper's arrest.
TNP also contacted SMRT yesterday about the latest development, but did not receive an official response at press time.
SMRT had been fined $200,000 for the 2011 breach.
Previous graffiti cases
Swiss national Oliver Fricker and his British accomplice Lloyd Dane Alexander cut through the fencing of the Changi MRT train depot and spray painted graffiti on a train.
Fricker was jailed seven months and given three strokes of the cane while Alexander remains at large.
SMRT was fined $50,000 for the breach.
German nationals Andreas Von Knorre and Elton Hinz snuck into the Bishan depot three times that month, vandalising a train on their last intrusion.
SMRT had to spend $6,500 on cleaning the train and another $7,150 to supervise the operation.
The affected train was taken off service for nine days, affecting more than 200,000 commuter trips, reported The Straits Times.
Von Knorre and Hinz were jailed nine months and given three strokes of the cane in March last year.